Directional clutch

ABSTRACT

The invention relates to a directional clutch with a drive element ( 10-120 ) and an output element ( 11;101, 102;130, 131 ) between which clamping elements ( 13, 14, 110 ) are arranged. Said clamping elements are connected to the output element in such a way that they turn without moving in relation to the direction of rotation of the output element both in a free-running position and in a torque transmitting position. The clamping elements are moved in a ring-shaped guide element ( 12 ) of the driving element in the free-running position and are blocked in said guide element ( 12 ) in the torque transmitting position. According to the invention, the output element consists of radial guides or borings ( 17;103, 104 ) each containing a projecting clamping body pin ( 15,16;111 ). In the first-mentioned case, the output element can be adjusted in an off-center position relative to the driving element. When adjusted in an offset position the clamping elements cyclically pass through a torque transmitting load path and a load-free path and transfer the occurring torque as they pass from the load-free path to the arched load path through non positive and/or positive engagement with the driving element.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. national phase of PCT application PCT/EP98/02809 filedMay 13, 1998 with a claim to the priority of German application 197 34962.5 itself filed Aug. 13, 1997.

FIELD OF THE INVENTION

The invention relates to a direction-controlled transmission(free-running clutch) with an input element and an output elementbetween which coupling elements such as coupling bodies, couplingrollers or coupling pawls are arranged that themselves or together withbodies connected to them both in the free-running position as in thetorque-transmitting position are connected in the rotation direction ofthe output element with same and which in the free-running position movein an annular guide of the input element and in the torque-transmittingposition are wedged on this guide.

BACKGROUND OF THE INVENTION

With prior-art known free-running or slip clutches, torque transmissiontakes place by means of pawls, coupling bodies, or balls that fitbetween the input and output elements. For example with a bicyclefree-running hub, balls are used so that if the input shaft turns fasterthan the housing, the balls are urged outward by the shape of grooves inthe shaft and wedge solidly between the input and output shafts so thatthe housing is entrained. If on the contrary the housing turns fasterthan the input shaft, the balls move inward in the grooves so that thereis no force transmission.

All these clutches have in common that the coupling element ispositioned radially between the input and output elements where iteither in the coupling position blocks relative movement between theinput and output elements or in the free-running position permitsrelative movement of the input element and the output element.

In order to make the free-running clutch simpler and cheaper tomanufacture even with these functions, German 2,452,650 proposes afree-running clutch with nonround coupling bodies between an inner andan outer coupling ring and out of contact when slipping with the fastercoupling ring, the coupling bodies each being held against the fasterring when slipping by means of a part-cylindrical surface parallel tothe body axis. The clutch has an inner coupling ring fixed on a shaftand a concentric outer coupling ring on another shaft concentric withthe inner ring. The gap between the two coupling rings holds nonroundcoupling bodies of which each has a bore extending parallel to its pivotaxis and by means of which it is mounted on a hardened pivot bolt. Theends of the pivot bolt projecting past the coupling bodies are eachforce fitted in a bore seat of an inner annular flange of the outercoupling ring. The bore in the one flange and the surface formed by thepivot bolt also form the coupling surface for the outer coupling ring.

WO 95/03503 describes a steplessly or almost steplessly variablepositive-contact planetary-gear transmission with input and outputelements that have several wheels that together form a planet wheel thatare in permanent mesh with a sun wheel. The ratios of the effectiveradii of the planet wheel and the sun wheel and the relative eccentricpositions of the planet wheel and the sun wheel which can be varied byvarious means determine the speed relationship between the input andoutput elements. The wheels forming the planet wheel cyclically run,when set eccentrically to the sun wheel, through a torque-transmittingload path and a load-free path, the wheels rotating both about theplanet-wheel axis and via respective one-way clutches about their ownaxes. On moving from the load-free path to the arcuate load path thewheels as a result of meshing block their actual rotation and transmitthe applied torque. Any irregularity in the torque transmission iscompensated for by variation of the radii determined by the load arcand/or the effective tangential component in a cyclical manner.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a new directionallycontrolled transmission that is simple to build and that permits thetransmission of considerable torque.

SUMMARY OF THE INVENTION

This object is attained by the transmission according to the inventionwhich is usable as a steplessly or almost steplessly variabletransmission or with no eccentric adjustability of the input elementrelative to the output element to provide a constant transmission ratiobetween the input and output elements. Basically however for both partsof the same embodiment the same advantages are usable to the same extentwith both solutions.

According to the invention the output element has radial guides in eachof which a projecting coupling-body pin or an element connected with thecoupling body is radially guided and the output element is moveableeccentrically to the input element, the coupling elements when eccentricmoving cyclically through a torque-transmitting load path or zone and aload-free path or zone and when moving from the load-free path to thetorque-transmitting load path the applied torque is transmitted from theinput element by force and/or structural engagement.

The claimed transmission includes embodiments where the input elementhas the described radial guide and the output element the annular guide.In a two-stage embodiment of a transmission one stage has the annulargroove or body and the following stage the radial-groove disk so thatstable phase positioning is obtained to reduce irregularities.

With this solution the coupling elements serve according to theinvention direction both as sliding as well as force-transmittingelements without any further parts such as balls or roller cages,coupling grooves, or other inertially working coupling parts beingnecessary. Wedging of the coupling elements is initiated in only onepart, namely the guide of the input element formed as an annular grooveor body, so that separate pivoting or mounting on the input or outputelements is not necessary. The hitherto necessary formation of an innerand an outer ring between which the coupling elements are mounted can beeliminated. In the simplest case the coupling elements themselves ortheir parts projecting out of the annular groove of the input elementare coupled rotationally to the output element. The invention includesalso embodiments where movable with the coupling elements in the guideor annular groove of the input element are bodies that are connectedwith the coupling elements and that serve as torque-transmittingelements rotationally coupled with the output element. The basic idea ofthe invention includes thus all arrangements where the coupling forcedoes not—as in the transmissions according to the state of theart—transmit forces between separate bearings and shafts, thereby givingthe advantage that only the substantially smaller tangential forcebetween the coupling elements and the guides is effective during torquetransmission.

In order to obtain with the transmission not only transmission ratios inthe neighborhood of 1:1 but also to provide other transmission ratios,the transmission is set up as a gear drive such that the output elementhas radial guides in each of which is arranged for radial movement aprojecting coupling-body pin or an element connected with the couplingbody, the output element being adjustable eccentrically relative to theinput element, the coupling elements running cyclically with eccentricpositioning through a torque-transmitting load path and a load-free pathin the described manner. In this manner one achieves stepless control ofthe rotation speed with good drive safety and a long service life. Speedvariations as can occur with V-belt transmissions as a result of slipare eliminated.

Thus the input element is a disk with generally radially extendinggrooves as radial guides or alternatively can have a sort of gear wheelas output element in the form of a shaft with radially projecting armswhose axial surfaces are formed as radial guides and that the respectiveprojecting coupling-body pins or the elements connected with thecoupling bodies when passing through the arcuate load path transmittorque to the arms and when passing through the load-free path areentrained by entrainment connections, preferably a wire or an elasticring, from the closest arm of the shaft. In this alternative arrangementthe spaces between the arms act as guides of the output element for theabove-described pins. The coupling elements themselves are moved inannular grooves of the input element about a pivot axis that is parallelor transverse to the pivot axes about which the coupling elements whenmoving from the torque-free to the torque-transmitting path aretippable. Torque can be transmitted through a single-end or double-endprojecting pin that is part of the coupling element and that engages ina seat (guide) of the output element. Alternatively it is also possibleto laterally hold the coupling element in the annular groove of theinput element with a fork that is jointly guided with the couplingelement in the annular groove, the fork having a pin on the side turnedaway from the coupling element that engages as described above in a seatof the output element.

As already described the annular guide of the input (or of the output)element is comprised of an annular groove in which the coupling elementcan slide or wedge or by a ring body that is gripped by slidable orwedgeable coupling elements or that is gripped frictionally by pivoting.

According to a particularly preferred embodiment the coupling element isso guided and shaped that it has only one degree of freedom necessary topivot from the load-free path to the torque-transmitting path. As aresult of this two-part transmission of force there is no canting of thecoupling elements since movements other than the desired tipping are notpossible. Both the pivot axis of the coupling element as well as therotation axis of the input element and of the output element aresubstantially parallel. In a concrete embodiment the projectingcoupling-body pin or an element connected with the coupling body has twoparts engaged in radial guides of the output element, the coupling bodypreferably having a pin projecting vertically from the surface of theannular groove and on whose end turned toward the coupling body isarranged a coupling-body pin with a longitudinal axis parallel to theannular groove and whose end fits in respective radial guides of a twopart output element, the two disks of the output element or the shaftwith parts formed as radially projecting arms being connected togetherand arranged to both sides of the input element.

The grooves of the disk-shaped output element are preferably madearcuate in order to obtain the greatest possible uniformity of torquetransmission with an eccentric offset. The coupling-body pins can beround or nonround in section.

Alternatively to the above-described embodiments, and particularly indrives where for space reasons a disk-shaped output element that iseccentrically movable relative to the input element is not desired ornot usable because of its size, it is possible to provide in theeccentrically movable output element a radially displaceable slide thatis rotationally coupled with the coupling body or a body coupledthereto. In this case the radially movable slide acts as an eccentricthat can be adjusted according to the set radial spacing from theinput-shaft axis to produce a different rotation speed of the outputelement.

As mainly described with respect to a planetary-gear drive that isprovided with conventional prior-art clutches, it is known to make thetransmission according to a further embodiment of the invention suchthat irregularities of torque transmission are compensated for byvariation of the effective radius defined by the effective load curveand/or the effective tangential component through cyclic at leastpartial adjustment. The coupling elements move successively in theannular groove with eccentrically offset input and output elements (orslide) through a torque-transmitting load path and a load-free path,torque peaks or other irregularities being catchable at the outputpoint. A first variant has already been described with reference toarcuately shaped radial grooves of the disk-shaped output element. It issimilarly possible to catch irregularities of slip control with elasticelements or, when using pawl-like slip elements, to control thetransmission ratio so as not to use tiny steps, but to select biggersteps of the transmission ratios so that the pawl or ramp width of thepawl-type free-running clutch are set such that there are no suddenchanges of load.

In a concrete embodiment of the invention the rotation conversionbetween the input element and the output element is effected in two ormore stages. To this end preferably the transmission means between thetwo stages, which preferably are formed as two disks, are formed aselastic connecting elements. The connecting elements can be knee leversthat carry out a cyclic controlled or spring-biased flexing. The actualknee levers can be guided in the load path radially by cams, formations,or multipart links or other mechanism. Irregularities of torquetransmission or of the transmission ratio can also be carried out by aforce-dependent spring biasing and/or by hydraulic, pneumatic, ormechanical counterweighting. With conversion in two or more stages thephase shift of the stages is set such that irregularities in the stagesare compensated against each other or the stages are out of phase withone another. With a two-stage drive the load path can be set so thatthey are offset by 180°. Preferably the number of coupling elements ineach drive stage with even-number stages is the same, while withuneven-number stages the phase offset is preferably done by a centralstar disk.

It is also possible in multistage drives to select clutches withrotationally opposite and/or switchable slippage or to use a reversingshaft or a controllable shaft with two parallel shafts.

Finally, the input element can be split such that a counterrotatingshaft and a planetary-gear adjusted shaft are hooked up as aplanetary-gear drive so that the driven (third) shaft of the planetarysetup can be adjusted by addition of the driven shaft steplessly with anincreased adjustment range.

The coupling elements that preferably are moved in the annular grooveabout a rotation axis tip when moving from the torque-free position tothe torque-transmitting position into a position where they frictionallyengage in the described annular groove. In this manner they run in theannular groove through a slide movement whose (slide) path is dependenton the path along which the coupling bodies move from the first line orpoint contact with the annular-groove wall to a small surface contact ofthe coupling element with the annular groove. This follows from Hertziantheory according to which pressing of substantially round bodies on aplane or a surface with a large radius of curvature produces flattening.Between the first contact of a coupling body and the annular groove andthe wedged position there is thus relative movement of the couplingelement (or the output element connected to it) and the input element.The slide path is indeed minimizable by choosing a material withextremely small deformation, but nonetheless influences efficiency andwear as a result of the considerable forces involved and the highswitching frequency during use as a stepless drive is influenced. Inorder to minimize wear of the coupling elements and to increase theefficiency of the transmission, the coupling elements are comprised of asingle- or multiple-part base and of a single- or multiple-part contactbody which wedge in the torque-transmitting position in the guide of theinput element. By replacing the one-piece relatively large coupling bodywith a multipart coupling element, the above-described slide path andthus the coupling-body wear created by use are minimized. The reductionof the slide path increases the efficiency of the transmission.

According to a further embodiment the contact body is comprised of oneor more rollers which when wedged and/or moving roll in the guide. Theactual rollers (contact bodies) are guided in the base and run whensliding in engagement with the annular groove or guide as rollers sothat there is very little running resistance. The transition from thetorque-free to the torque-transmitting path, that as is known isassociated with a deformation of material (flattening of thewedged-together surfaces) is as a result not critical since with thisthe rolling takes place with negative acceleration until the two partsare not moving relative to each other. The forced rolling ensures thatthe wedging together of the surfaces changes so that the service lifeand safety is increased with less wear (pitting).

Biasing in a contact position that is necessary for an accurate wedgingor dead path is effected preferably by at least one spring which bearsdirectly or indirectly on the contact body in a direction pressing thecontact body on the groove walls.

Preferably the spring or wedging elements connected hereto, preferablyrollers or balls, are braced on surfaces of a further annular groovethat is formed in a floor of the annular groove. A pin or roller cantravel in this annular groove and presses via a spring connectedtherewith with the contact body. Such an arrangement preferably makes itpossible to form particularly narrow coupling elements (coupling bodies)that allow one to accommodate more coupling bodies in each input andoutput disk without them coming into contact with one another inparticular eccentric positions.

According to a further embodiment of the invention the contact bodieseach have an axially directed pin that engages in a seat of the outputelement for transmitting torque. According to a further embodiment ofthe invention both contact bodies of a coupling element have an axiallyprojecting pin and are thus axially shiftable and alternatively only oneof the pins serves for transmitting torque. In this manner one achievessimple switching of the slip direction according to which pin of the twocontact bodies engages in a seat of the output element.

Instead of the described rollers or balls in a further embodiment of theinvention particularly intended for transmitting of particularly hightorques, contact bodies are used with a nonround cross section that havea surface portion that generally corresponds to the shape of the annulargroove which it engages frictionally when in the torque-transmittingposition. With this arrangement it is admittedly no longer possible forthe contact body to roll, but there is, instead of the line contactproduced by a roller or ball when moving into the wedged position, fullsurface contact that can take higher loads. In practice as a result,contact forces can be increased by a factor of 10² with a correspondingincrease in transmittable torque. On the inner side, that is directedtoward the base, the shape of the contact can be made such that in thewedged condition there is surface contact which can take during torquetransmission loads that are greater by a multiple. Preferably thesurface of the contact body that is in surface contact with anannular-groove wall for frictional contact has a radius of curvaturewhich corresponds to the radius of curvature of the annular-groove wall,the ratio of these radii being to minimize Hertzian pressure between0.6:1 and 1.4:1, preferably between 0.8:1 and 1.2:1. In the rangebetween light contact to full wedging (torque-transmitting position) thecontact bodies do not slip and lie without moving on the annular-groovesurfaces while the rotation of the parts of the base that is necessaryto take up the normal forces forms at all locations a low-loss andlow-friction rolling movement. Preferably the shapes between the basebody and the contact body, which are opposite each other, are circular.

The biasing thus takes place by spreading of the contact bodies (orcontact surfaces) with a spring or elements connected thereto which arebraced in a further annular groove in the base of the annular groove.

Since the coupling angle at about 4° for wedging (coupling angle smallerthan the arctan of the coefficient of friction) is very small, thecoupling bodies are in principle very sensitive to tolerances and wear.Thus as soon as, because of wear, the overall length of the couplingbody has grown smaller than the coupling gap, there is the danger thatthe coupling bodies invert. In order to prevent this according to afurther embodiment the invention the base is formed of two parts thatengage each other with opposite surfaces that are convex, preferablyformed as a logarithmic spiral. As a result the height of the couplingbody can be maintained constant when the contact body has worn down to ashorter height. The thus increasing rotation of the contact body whenwedging thus produces an automatic adjustment.

In order to avoid rotation of the described coupling elements in orderto minimize the sensitivity to tolerances and wear, according to afurther embodiment of the invention the contact bodies are formed ascoupling rollers that are guided on a base that is prevented fromrotating relative to a central axis of the groove, preferably by pins insleeves connected with it and that are guided in an annular groove ofthe input element. The opposite sides of the base on which one of thecoupling rollers engages extend diverging toward one end, theypreferably being formed of circular shape and constructed of circleswhose radii are essentially the same size both offset from the actualcontact point of the base with the respective coupling roller by anangle, preferably below 10° and further advantageously pivoted by 4° inthe opposite direction.

In order to decrease slip-entraining torques in the slip mode further,according to a further embodiment of the invention the coupling bodiesare not spring-biased but are only engaged on the location where theymust be locked by a stationary spring, an air or lubricant stream, or amagnet.

Preferably the transmission can be set as an adjustable drive formotor-vehicle accessories such as air conditioners, lights, or the like.The described accessories are driven according to the state of the artby means of a v-belt drive so that the instantaneous engine speeddetermines the rotation speed of the accessory drive. With an airconditioner it is clear that when idling there is inadequate cooling ofthe passenger compartment which is more noticeable since motion-inducedventilation are not or are only slightly reduced. A controllable driveaccording to the invention can provide relief by increased output speed.The same is true for the lights or other subassemblies.

The alternative solution is characterized in that the output and inputelements are each formed as two parts, that is each with two axiallyoffset parts, the input or the output element being formed of twoaxially offset disks with bores in each of which engages a projectingcoupling-body pin or element connected therewith such that a tangentialforce and thus torque can be transmitted between the pin and the diskand so that with a generally mirror-symmetrical arrangement of the inputand the output element a generally homogenous stress distribution isobtained. Unlike the other solution the radial distance of the describedcoupling-body pins to the input and the output shafts is constant.Except for the parts that serve for the eccentric offsetting of theinput and output elements, this embodiment operates like theabove-described systems.

Preferably the coupling elements are comprised of a single- ormultiple-part base and of a multiple-part contact body which wedge inthe torque-transmitting position in the guide of the input element, thecoupling surfaces of the contact bodies being part circular so thatsurface contact is produced generally in the contact zone with the ringdisk, the Hertzian pressure being minimized by matching radii of thecontacting surfaces of the ring disk and the contact body. The ratio ofthe radius of the contact-body surfaces and the radius of the ring diskthat engage each other frictionally in the torque-transmitting positionlies between 0.6:1 and 1.4:1, preferably between 0.8:1 and 1.2:1.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention are shown in the drawings. Therein:

FIGS. 1 and 2 are perspective views of a transmission according to theinvention

FIG. 3 is a top view of an output element;

FIG. 4 is a partial sectional view through a transmission acting as adrive unit;

FIG. 5 is a multistage drive unit;

FIGS. 6a and 6 b are top and sectional views of a drive unit accordingto the invention usable for a bicycle;

FIGS. 7a and 7 b are top and sectional views of a drive unit accordingto the invention formed as a planetary-gear drive;

FIGS. 8 and 9 are top and sectional views of a drive unit according tothe invention as a drive for an auxiliary device;

FIG. 10 is a top view of an input element with a coupling element guidedin a groove;

FIG. 11 is a diagram of an input element and an output element withseveral coupling elements;

FIG. 12 is a diagram of a multistage drive according to FIG. 11;

FIG. 13 is a top view of an input element with another embodiment of acoupling element;

FIG. 14 is a corresponding enlarged illustration of the coupling elementaccording to FIG. 13;

FIGS. 15 to 18 illustrate further embodiments of a coupling element;

FIG. 19 is a further embodiment of a transmission according to theinvention in a perspective view;

FIG. 20 is a partial top view of the FIG. 19 embodiment in enlargedview;

FIG. 21 is a further embodiment of the transmission according to theinvention;

FIG. 22 is an embodiment of a transmission according to the inventionwith an annular guide for the coupling element;

FIG. 23 is an enlarged perspective view of a coupling element; and

FIG. 24 is a perspective view of an alternative embodiment according tothe invention.

SPECIFIC DESCRIPTION

The transmission shown in FIGS. 1 and 2 has a disk input element 10 andan output element 11. The input element 10 has an annular groove 12 inwhich coupling elements 13 and 14 are moved circularly. These couplingelements 13 and 14 each have a projecting pin 15 whose enlarged end 16is seated in radially extending grooves 17 of the element 11. With theinput and output disks 10 and 11 coaxial the transmission ratio is 1:1,the parts acting as coupling elements circulating freely in the groove12 in the freewheel mode. In the coupling mode the coupling bodies wedgein the groove 12 so that torque applied to the disk 10 is transmitted tothe output disk 11. The radial position of the coupling bodies 13 and 14and the pin 15 or the enlarged head 16 is shown by way of example inFIG. 3 for a transmission ratio of 1:1.

When the input disk 10 is eccentric to the output disk 11 the angular ortangential offset of the coupling bodies 13 in the groove 12 changes asshown in FIG. 4. The coupling bodies 13 thus pass through atorque-transmitting load path (in the upper region of the groove 12) anda load-free path (in the lower region of the groove 12). The pins 15 ortheir enlarged heads 16 can according to the eccentric offset moveradially in the groove 17 but they remain rotationally coupled with theoutput disk 11. Movement of the coupling bodies 13 from the lockedcondition into the free-running condition is assisted by spring-loadedpins 18 as is known in free-running clutches according to the state ofthe art.

The transmission used as a two-stage drive unit is shown in FIG. 5. Inthe illustrated embodiment the rotation of an input shaft 19 istransmitted to an input disk 20 whose annular groove 21 holds couplingbodies 22. These coupling bodies 22 have axially projecting pins 23 thatengage in radial grooves 24 of a star disk 25 so that rotation of theinput disk 20 is transmitted in the coupling mode of the coupling bodiesto the star disk 25. The star disk 25 is made mirror symmetricalrelative to a transverse plane and has, in line with the annular grooves24, annular grooves 26 on the opposite side in which engage respectivepins 27 of coupling bodies 28 that are circularly movable in acorresponding annular groove 29 of an output disk 30. In the couplingmode of the coupling elements 28, rotation of the star disk 25 istransmitted via the output disk 30 to the output shaft 31.

The above-described principle can be used in various manners within thescope of the invention. Thus according to the embodiment of FIG. 1 thecoupling bodies can be so arranged that the coupling mode is initiatedby a rotation about an axis that is parallel to the rotation axes of theinput and output elements 10 and 11 or—as shown in FIG. 2—by rotationabout an axis that is substantially perpendicular to this rotation axis.It is further possible that instead of a star disk with radial grooveson both sides to make this disk such relative to the input disk 20 andoutput disk 30 that the disks 20 and 30 are on one and the same side sothat one of the disks 30 engages radially over the other. Such anembodiment is shown in the planetary drive unit of FIGS. 7a and 7 b. Therotatable disk 32 has grooves 33 in which are engaged both the pins 34of the radial grooves 35 of the input disk 36 as well as the pins 37 ofthe coupling bodies which are engaged or guided in radial grooves 38 ofan annular output disk 39. Rotation of the output disk 39 is transmittedvia a gear 40 to a gear wheel 41 on an output shaft 42. In theembodiment shown in FIG. 7b a hydraulic cylinder 42 serves for theeccentric positioning of the disk 32. On such eccentric positioning ofthe disk 32 the rotation of the input shaft 43 is transformed accordingto the eccentric offset corresponding to the drive parameters intodifferent-speed rotation of the output disk 32.

According to the embodiment of FIGS. 6a and 6 b which is formed as abicycle planetary-gear transmission, the coupling-body pins are held ina radially movable slide 44 that takes the place of the output diskformed with radial grooves. Radial shifting of the slide 44 can changethe transmission ratio.

An embodiment usable as a drive for accessories or a power takeoff isshown in FIGS. 8 and 9. Rotation inputted by an input shaft 45 istransmitted by means of a disk 46 and coupling bodies 47 that aremovable circularly or wedgeable in corresponding annular grooves to adisk 48 that is movable eccentrically of the axis of the shaft 45 forexample from position 49 to position 50. In this manner the pins 52 ofthe coupling elements anchored in a pulley 53 and engaged in the radialgrooves 51 of the disk 48 change the transmission ratio according toeccentric offset. Instead of a hydraulic adjuster the eccentric offsetis set by a servomotor (controllable stepping motor or the like).

Further variations, in particular aimed at compensating forirregularities in transmitting torque are addressed as described in WO95/03503, it being understood that instead of the one-way clutchesaccording to the prior art the transmissions according to the inventionare used.

As shown in FIG. 10 the coupling element 13 that can slide or wedge in agroove 12 of the input element 10 is formed of several parts, namely acontact body formed of a base 60 and two rollers 61 and 62 whose forcepresses the rollers 62 and 61 against walls of the groove 12. The base60 is provided with an axially projecting pin 15 that engages in acorresponding recess of an output element, preferably in a groove 17(see FIGS. 1 and 2).

The illustration of FIG. 11 shows a further embodiment where the base 60is connected with a pin 68 that is guided in a groove 70 that isarranged in the floor of the annular groove 12. The contact bodies arerollers 61 and 62 which ride along the walls of the groove 12. Thisembodiment can according to FIG. 12 be set up as a multispeed drive unit(here with two input and output disks 10 and 11).

A further embodiment is shown in FIGS. 13 and 14. The base is hereformed of two parts 71 and 72 which as shown in the sectional view formseats with their ends turned toward the walls of the groove 12 receivingcomplementary portions of contact bodies 73 and 74 which can be urged bya spring 63 into the coupling position with the input element formed bythe disk 10. The surfaces of the contact bodies 73 and 74 engaging thewalls of the groove 12 have the same radius of curvature as these walls.In this manner substantial surface contact is obtained.

FIGS. 15 and 16 show an embodiment with a one-piece base 66 that has onopposite sides contact bodies 73 and 74 as described above incorresponding seats.

In the embodiment according to FIG. 17 rotation of the coupling body iscompletely eliminated so that problems with respect to tolerances andwear are substantially reduced. To this end the coupling rollers 64 and65 are mounted on a base 75 which in turn is prevented from rotating bypins 76 and 77 provided with sleeves 78 and 79 riding in a groove 83 ofthe input element 10. The surfaces of the base 75 turned toward thecoupling rollers 64 and 65 are such that in any position in which thecoupling rollers 64 and 65 wedge because of wear, tolerances, orelasticity, the same coupling angle is produced. In the embodiment ofFIG. 17 the shape is shown by the dashed lines 86 and 87. Thecorresponding concave surfaces 84 and 85 of the base 75 can be shapedsuch that initially circles centered on the input element 10 are drawnthrough the respective contact points P between the coupling rollers 64and 65 with the base body 75 and the circle is then shifted by theactual coupling angle, for example 4°, from this point so that the basebody 75 forms a narrowing ramp with the annular groove 12 in which thecoupling bodies 64 and 65 roll. At point P the base 75 has a height withzero tolerance, that is the difference between the coupling groovedimension minus both roller diameters is the nominal dimension. Wiresprings 88 and 89 that are connected at one end with the base 75 servefor pushing out the coupling rollers 64 and 65.

FIG. 18 shows a further development of the embodiment according to FIG.13 wherein the upper base part and the respective coupling body are notshown for clarity of view. In the embodiment of FIGS. 13 (and 14) thereis the disadvantage that with an assumed wedge angle of 4° the length ofthe coupling body is only larger than the gap by a factor of 1/(cos4°)=1.002442. With a coupling-gap width of e.g. 10 mm thus the couplingbody is only about 2.4/100 mm longer than the coupling gap which meansthat with modest wear or slight elasticity in the coupling body or inthe annular groove the coupling angle decreases drastically and in somecircumstances can be less than 0 so that the coupling body slips.

In order to deal with this the surface 80 where the two bases 71 and 72engage each other and which roll off each other when the coupling angleα changes is not circular but is of greater radius of curvature withincreasing coupling angle α. The recess for the pin 15 serves only fortransmitting the torque, the normal forces of the coupling action aretransmitted directly via the base bodies 71 and 72 to each other.

The shape 80 of the mutually engaging surfaces of the bases 71 and 72can be shaped iteratively out of the fan-like support radii with eachsucceeding radius being turned relative to the preceding one by 4°mathematically about the same center. Each succeeding radius increasesin length by the factor 1/(cos 4°) (assuming that the coupling angle is4°; otherwise any other angle is used). The effective overall height ofthe coupling body thus increases as the coupling angle α decreasessince, when the two bases 71 and 72 roll off each other on the surface80, the support radii become bigger at the instantaneous contact point.The surface 80 is preferably shaped in section as a logarithmic spiralas shown in FIG. 18. Alternatively other shapes can be employed withwhich the wear characteristics or the elasticity of the parts or otherinfluences which affect the angle α of the coupling action can be setsuch that a sure wedging without the danger of slipping is obtained.

In the system of FIG. 19 the output element is formed by two disks 101and 102 which are connected together by a common shaft. These disks 101and 102 have respective radial grooves 103 and 104 formed as radialguides for ends of coupling-body pins 111 of a coupling body 110 that iscomprised of the actual coupling body 112 that can tip in an annulargroove of the input disk 120 and that further is formed of a pin 113extending transversely out of the annular-groove surface and a pintransverse thereto whose ends 111 extend past the ends of the inputelement 120. The parts 112, 113, and 111 are formed as one piece. Thecoupling body 110 has as a result of the selected radial guides 103 and104 of the two star disks 101 and 102 only a single degree of freedom,namely that it can pivot from the torque-transmitting position into theslip position about the longitudinal axis of the pins 111, and the tworotation axes of the output elements 101 and 102 and of the inputelement 120 are parallel. Canting of the coupling body 112 by tipping inanother direction is thus effectively ruled out.

Instead of the disk-like output elements 101 and 102 according to FIG.21 an output element can be used that is formed with teeth and that iscomprised of a shaft 130 from which arms 131 extend radially. The arms131 are tipped relative to a perpendicular from the surface of the shaft130 by 40° to 50°. The coupling elements 110 are made the same as inFIG. 19 and run circularly in the radial-groove guides of thedisk-shaped input element each of whose faces is juxtaposed with anoutput element formed by the parts 130 and 131. The arms 131 are actedon in the load-arc path by the pins 111 of the coupling element with theapplied torque. In the load-free path, that is in the free-runningphase, the coupling body 110 is entrained by an unillustrated wire orelastic ring by the arms 131. The output element 130, 131 is movableeccentrically relative to the input element 120.

Preferably each pin 111 is formed as a rotatable sleeve in order tominimize frictional losses.

The geometry of the interacting annular groove and the arms 131 ispreferably such that torque transmission through the pins 111 only takesplace close to the shaft 130. Torque transmission which according toFIG. 21 takes place in the right-hand side of the illustration (load-arcpath) is via the pins 111 on the arms 131 in the arm portions that arecloser to the shaft 130 while the outer portions of the arms are notsubject to torque. In the load-free path on the left of the illustrationthe outer tips of the arms 131 are only stressed enough to entrain thecoupling elements or pins 111 via elastic connections with the arms.

Since instead of the above-described radial grooves 12 the spacesbetween the arms 130 form the radial guides, the annular groove 12 mustbe made correspondingly wide so that its inner diameter is equal to thediameter of the shaft 130 and the desired extent of eccentric offset ofthe input element to the output element.

Of course in a transmission according to FIGS. 10 to 21 couplingelements as described above and shown in FIGS. 11 to 18 can be used.

As shown in FIGS. 22 and 23, this transmission embodiment uses insteadof an annular groove a coupling ring 200 which in the coupling modetransmits torque via the coupling stones 210 and 211 by friction. Thecoupling stones 210 and 211 each ride in a concave seat of a respectivebody 212 and 213. The curved face of the coupling stone 211 matches theradius of the outer edge surface 201. The same is true for the inneredge surface 202 which corresponds to the radius of the slightly convexface of the coupling stone 210. The part 212 has roller pairs 215 and216 that roll on the corresponding annular surfaces of the groove 217 inthe free-running position. Tipping of the coupling element shown in FIG.23 presses the coupling stones in surface contact on the annular edgesurfaces 201 and 202. The bolt 218 lies in the bore and projects past atboth ends so that its ends can be guided in radial grooves as describedabove. The use of a coupling ring 200 instead of a coupling grooveholding coupling bodies has the advantage that the coupling ring is onlysubjected to compression and not to bending stresses so that even whenmade small the input and output disks can transmit considerable torque.This prevents that when wedged the coupling elements “bend out” theannular groove. Otherwise this embodiment functions the same as those ofFIGS. 1 to 21.

The embodiment shown in FIG. 24 has an input shaft 220 and an outputshaft 221 which are journaled on each other via a roller bearing 222.Torque is transmitted in the coupling mode from the coupling ring 200via the contact bodies (coupling stones) 210 and 211 and the bases 212through the coupling-body pin 218 that is guided in bores 224 of thedisk 223 on the shaft 221.

The transmission according to FIG. 24 is preferably (ignoring theeccentric adjustability of the input element) so constructed relative tothe output element as shown in FIG. 19 and described above, thus in twopieces. The output element thus has two disks 223 that are arrangedmirror-symmetrical to each other relative to the axis. Correspondinglythe input element is made in two pieces. This construction facilitates atangential force and thus torque transmission between the coupling-bodypins 218 and the respective disks 223 in a symmetrical arrangement so asto produce a generally homogenous force distribution on the activecontact zones of the annular disks.

The bores 218 as well as the bearings can thus be constructed to cancelout tolerance problems with respect to alignment and running between thetwo shafts 220 and 221 without thereby influencing the functioning ofthe clutch action of the coupling bodies.

In addition the construction of the coupling elements corresponds tothat shown and described with reference to FIGS. 22 and 23.

Where in the above description the output element is described as a diskwith radially extending grooves and the input element as a disk with anannular groove or an annular body, the scope of the invention in ananalog manner includes embodiments where the output element has annularguides and the input element is a disk with radially extending grooves.

What is claimed is:
 1. A variable-speed transmission comprising: a firstelement rotatable about a first axis and having an annular guidecentered on the first axis; a second element rotatable about a secondaxis parallel to the first axis and having a plurality of radiallyextending arms having edges forming respective angularly spaced andradially extending guides; respective coupling bodies angularly spacedabout the axes and each having one part engaged with a respective one ofthe radial second-element guides and another part engaged with theannular first-element guide, the other parts being constructed such thatthey can slide in one angular direction relative to the annular guidebut not in an opposite angular direction relative thereto; and means forradially displacing one of the elements relative to the other elementinto a position with the second and first axes offset from each otherfor, on relative rotation of the first element in the one directionrelative to the second element, orbiting the bodies through atorque-transmitting zone close to the second axis and wedged on theannular first-element guide and through a free-running zone remote fromthe second axis and sliding on the annular first-element guide, wherebyon traversing the torque-transmitting zone the bodies rotationallycouple the first and second elements.
 2. The variable-speed transmissiondefined in claim 1 wherein the first element is a disk and the annularguide is an axially open groove formed in the disk.
 3. Thevariable-speed transmission defined in claim 1 wherein the annular guideis a ring and the bodies each have two members engaging radial inner andouter faces of the ring.
 4. The variable-speed transmission defined inclaim 1 wherein the second element is a disk and the radial guides areaxially open grooves formed in the disk.
 5. The variable-speedtransmission defined in claim 1 further comprising respective springsurging the bodies into engagement with the annular guide.
 6. Avariable-speed transmission comprising: a pair of first elements spacedapart along and rotatable about a first axis and having respectiveaxially confronting annular guides centered on the first axis; a secondelement rotatable between the first elements about a second axisparallel to the first axis and having a plurality of angularly spacedand radially extending guides; respective coupling bodies angularlyspaced about the axes and each having one part engaged with a respectiveone of the radial second-element guides and a pair of axially alignedfirst pins engaged with the respective annular first-element guides, theother parts being constructed such that they can slide in one angulardirection relative to the annular guide but not in an opposite angulardirection relative thereto; and means for radially displacing one of theelements relative to the other element into a position with the secondand first axes offset from each other for, on relative rotation of thefirst element in the one direction relative to the second element,orbiting the bodies through a torque-transmitting zone close to thesecond axis and wedged on the annular first-element guide and through afree-running zone remote from the second axis and sliding on the annularfirst-element guide, whereby on traversing the torque-transmitting zonethe bodies rotationally couple the first and second elements.
 7. Thevariable-speed transmission defined in claim 6 wherein the firstelements are disks and the annular guides are axially open andconfronting grooves formed in the disks.
 8. A variable-speedtransmission comprising: a first element rotatable about a first axisand having an annular guide centered on the first axis; a second elementrotatable about a second axis parallel to the first axis and having aplurality of angularly spaced and radially extending guides; respectivebases radially displaceable in the guides; respective coupling bodiescarried on the bases and each having a part engaged the annularfirst-element guide and constructed such that the parts can slide in oneangular direction relative to the annular guide but not in an oppositeangular direction relative thereto; and means for radially displacingone of the elements relative to the other element into a position withthe second and first axes offset from each other for, on relativerotation of the first element in the one direction relative to thesecond element, orbiting the bodies through a torque-transmitting zoneclose to the second axis and wedged on the annular first-element guideand through a free-running zone remote from the second axis and slidingon the annular first-element guide, whereby on traversing thetorque-transmitting zone the bodies rotationally couple the first andsecond elements.
 9. The variable-speed transmission defined in claim 8wherein each coupling body comprises a pair of members pivoted on therespective base about axes parallel to the first and second axes, themembers bearing on respective sides of the annular guide.
 10. Thevariable-speed transmission defined in claim 9 wherein the members bearradially on each other.